Tagequity

Use Turf to perform GIS functions in a web browser

Turf's merge function joins invisible buffers around each Divvy station into a single, super buffer.

Turf’s merge function joins invisible buffers around each Divvy station into a single, super buffer –all client-side, in your web browser.

I’m leading the development of a website for Slow Roll Chicago that shows the distribution of bike lane infrastructure in Chicago relative to key and specific demographics to demonstrate if the investment has been equitable.

We’re using GitHub to store code, publish meeting notes, and host discussions with the issues tracker. Communication is done almost entirely in GitHub issues. I chose GitHub over Slack and Google Groups because:

  1. All of our research and code should be public and open source so it’s clear how we made our assumptions and came to our conclusions (“show your work”).
  2. Using git, GitHub, and version control is a desirable skill and more people should learn it; this project will help people apply that skill.
  3. There are no emails involved. I deplore using email for group communication.*

The website focuses on using empirical research, maps, geographic analysis to tell the story of bike lane distribution and requires processing this data using GIS functions. Normally the data would be transformed in a desktop GIS software like QGIS and then converted to a format that can be used in Leaflet, an open source web mapping library.

Relying on desktop software, though, slows down development of new ways to slice and dice geographic data, which, in our map, includes bike lanes, wards, Census tracts, Divvy stations, and grocery stores (so far). One would have to generate a new dataset if our goals or needs changed .

I’ve built maps for images and the web that way enough in the past and I wanted to move away from that method for this project and we’re using Turf.js to replicate many GIS functions – but in the browser.

Yep, Turf makes it possible to merge, buffer, contain, calculate distance, transform, dissolve, and perform dozens of other functions all within the browser, “on the fly”, without any software.

After dilly-dallying in Turf for several weeks, our group started making progress this month. We have now pushed to our in-progress website a map with three features made possible by Turf:

  1. Buffer and dissolving buffers to show the Divvy station walk shed, the distance a reasonable person would walk from their home or office to check out a Divvy station. A buffer of 0.25 miles (two Chicago blocks) is created around each of the 300 Divvy stations, hidden from display, and then merged (dissolved in traditional GIS parlance) into a single buffer. The single buffer –called a “super buffer” in our source code – is used for another feature. Currently the projection is messed up and you see ellipsoid shapes instead of circles.
  2. Counting grocery stores in the Divvy station walk shed. We use the “feature collection” function to convert the super buffer into an object that the “within” function can use to compare to a GeoJSON object of grocery stores. This process is similar to the “select by location” function in GIS software. Right now this number is printed only to the console as we look for the best way to display stats like this to the user. A future version of the map could allow the user to change the 0.25 miles distance to an arbitrary distance they prefer.
  3. Find the nearest Divvy station from any place on the map. Using Turf’s “nearest” function and the Context Menu plugin for Leaflet, the user can right-click anywhere on the map and choose “Find nearby Divvy stations”. The “nearest” function compares the place where the user clicked against the GeoJSON object of Divvy stations to select the nearest one. The problem of locating 2+ nearby Divvy stations remains. The original issue asked to find the number of Divvy stations near the point; we’ll likely accomplish this by drawing an invisible, temporary buffer around the point and then using “within” to count the number of stations inside that buffer and then destroy the buffer.
Right-click the map and select "Find nearby Divvy stations" and Turf will locate the nearest Divvy station.

Right-click the map and select “Find nearby Divvy stations” and Turf will locate the nearest Divvy station.

* I send one email to new people who join us at Open Gov Hack Night on Tuesdays at the Mart to send them a link to our GitHub repository, and to invite them to a Dropbox folder to share large files for those who don’t learn to use git for file management.

HOT lanes and equity

The following is extracted from a paper I wrote about I-15 Express Lanes (first phase in 1998) and Managed Lanes (second phase, still under construction). Read the paper, Implementing value pricing on a highway in Southern California.

Equity

Political support is necessary for any value pricing application. Mayor Jan Goldsmith’s story of political maneuverings gave that indication. Implementing value pricing is politically difficult to implement because of the high opposition from the public. This is because of the costs borne by the user. In the case of I-15 Express lanes, all users have the opportunity to use the express lanes if they ride the bus, a motorcycle, ride with a friend or coworker, or drive an exempt low-emission vehicle. There are several tollways around the United States and the world which don’t have a free alternative.

Weinstein and Sciara (2006) suggest that we should avoid defining whether or not the HOT lane concept is equitable, but instead how to address perceived equity issues. The pair have written two reports for planners who will potentially work on value pricing projects. Both reports are cited in this section.

It has been found in the I-15 Express lanes application that users who never use the express lanes, and only use the main lanes (free lanes) occasionally benefit from the lane shift of users to the Express lanes. (Supernak, et al. 1998)

Another concern is that low-income drivers, who cannot afford to pay for the express lanes, will disproportionately benefit high-income drivers (Weinstein and Sciara 2006, 179). This debate between rich and poor drivers has emerged under the title of “Lexus lanes”, but the arguments calling HOT lanes a fast lane for the wealthy are unfounded:

a. Users from all income groups use the express lanes on I-15 and find it fair. The final report’s (Supernak 1999) attitudinal survey found that within all income groups, a majority of respondents approved of the FasTrak tolling of solo drivers in the I-15 HOV lanes.

b. As a mitigation measure to this perception, the Express lanes operation is paid for entirely by toll revenue, which also pays for increased express bus service. Oddly, though, Calfee and Winston (1996) found that the way toll revenues are used does not affect commuters’ willingness to pay (WTP), suggesting that these two mitigation measures do not affect public perception.

Works Cited

Calfee, John, and Clifford Winston. “The value of automobile travel time: implications for congestion policy.” Journal of Public Economics 69 (1998): 83-102.

Supernak, Janusz, Jacqueline M Golob, Kim Kawada, and Thomas F Golob. “San Diego’s I-15 Congestion Pricing Project: Preliminary Findings.” Institute of Traffic Studies, University of California, Irvine, Irvine, 1998.

Weinstein, Asha, and Gian-Claudia Sciara. “Unraveling Equity in HOT Lane Planning: A View from Practice.” Journal of Planning Education and Research 26 (2006): 174-184.

I’ve graduated

Say hello to Chicago’s newest planner. ME!

Instead of walking at my school’s graduation ceremony on May 7, 2010, I was busy at work making sure bike parking in Chicago is equitably distributed, visiting the Pacific Northwest, and generally having fun.

Me having fun riding a Volae recumbent bicycle at the Rapid Transit Cycleshop grand opening in University Village at UIC’s South Campus.

Did I say something about bike parking equity? Oh, yeah, I’ve only blogged about it here a couple of times before and it comprised my entire master’s project (which thankfully was approved and deemed “satisfactory” by my wonderful adviser, Vonu). You can read the entire project on my website. I wrote my project in a wiki called DokuWiki – it’s a text-based, lightweight application that encourages writing and doesn’t stand in the way of a creative masterpiece (like Microsoft Word does).

It’s a huge project (there are over 35 webpages that come out to 139 printed pages). I realize that most people won’t read it, but in the course of preparing for a short presentation I recently gave to some staff members at Active Transportation Alliance, I created a short summary to aid me.

Read my project, Bike Parking Equity, or the summary.

A photo of my cheaply printed project. I printed to PDF each and every webpage in the project and then combined them all, using the Mac’s built-in functionality and Preview application.

Igniting the discussion on equity

I want to have more conversations about transportation equity

My master’s project is all about it. You might have read me talking about it a little here two weeks ago. A then I shot off a post with some key quotes I’m using about the topic in my project.

The purpose of the map is to show the difference in distribution between 2008 and 2009.

This post, though, is all about the graphic above. A lengthy conversation has begun in the comments on the Flickr page. I want more people to get talking about why 2008 might look the way it does, and why 2009 looks the way it does. Perhaps you need a little background on 2009: I made sure to visit the most underserved Wards you see in 2008 and ensure they receive new bike racks in 2009.

A big question is why people in those areas aren’t asking for bike racks. Does no one there ride a bike to the store? Or maybe they do but don’t know how to request a bike rack or know the purpose of one? Maybe they got a bike stolen and need some tips on proper locking.

Those are all questions I want my project to answer – and I’m working hard 20 hours per week to answer them! But I want more questions. I want ideas that point me to look in new directions. If you don’t like my response, tell me.

Bike parking is almost always mentioned in nationwide bike plans as a necessary way to complete the urban bicycling network. Mia Birk, “famous” bicycle planner, and principal at Alta Planning and Design in Portland, Oregon, says that bike parking is part of “the tool kit for successful 
bicycle infrastructure in cities.” Another Portland entity is aware of equity: BikePortland.org.

What’s going on here? Photo by Eric Rogers.

Quotes about transportation equity

My master’s project involves a discussion about equity. Equity of bike parking distribution is the main focus of my project.

I picked up some great books at my school’s library. Here are some selected quotes (many of which I’ll use in the project’s paper).

  • “Transportation improvements distribute nonuniformly over space, implying that they affect diverse populations disproportionately” (Berechman).
  • “Geography defines the contours of the equity analysis in two important ways. First, since investment in transportation infrastructure is geographically specific, there is inherent competition and conflict between places” (Hodge).
  • The “costs and benefits of transportation policies may take place in different time periods” (Bae and Mayeres). For example, “mega projects are often built with excess capacity aimed at satisfying future needs. Such a pattern imposes inequitable intergenerational transfers, favoring the future rather than the present generations” (Berechman).
  • “Indirect benefits…represent real impacts that probably benefit some people more than others. It is exceedingly difficult, however, to trace through the benefit stream of these broad impacts” (Hodge).

And my favorite: “Transportation is an unusual public service in that it is not consumed for its own sake but, rather, as a means to another end. Thus, the value of the service depends primarily on how well it provides access to other places” (Hodge).

My professor last semester said the same thing, actually, and then we had a huge discussion trying figure out situations where this isn’t true. The only thing our class (well, the professor himself) could come up with was joyriding (driving aimlessly in a car). But is joyriding really transportation? The trip origin and destination are the same and the trip has no purpose.

I thought of the transportation system at Walt Disney World, but I eventually withdrew my support – although the goal of that system is to make it easy for guests to spend more money, the system has a legitimate role in giving access to places inside and outside the “pay area.”

Sources

Bae, Chang-Hee Christine and Inge Mayeres. “Transportation and Equity.” Donaghy, Kieran P, Stefan Poppelreuter and George Rudinger. Social Dimensions of Sustainable Transport: Transatlantic Perspectives. Burlington: Ashgate Publishing Company, 2005. 164-192.

Berechman, Joseph. The Evaluation of Transportation Investment Projects. New York City: Routledge, 2009.

Hodge, David C. “My Fair Share: Equity Issues In Urban Transportation.” The Geography of Urban Transportation. Ed. Susan Hanson. Second. New York City: Guilford Press, 1995.

Benefits of bike parking

I’m working on my master’s project about bike parking distribution and equity in Chicago and while working on a section in the paper, I decided to get some help from readers. Many transportation projects are measured on predicted changes like trip travel time savings or trip cost savings (I give two examples below the photo).

My question is this: What are a bike parking installation’s measurable benefits to a traveler or a community?

Photo: Portland has installed 40 on-street bike parking “corrals” since 2004. What does a traveler or community gain from this bike rack installation? Photo by Kyle Gradinger.

To figure equity (fairness) for these project types, you measure these impacts for different groups (often high, medium, and low income), either in the alternatives analysis, or project selection phases. So, converting a lane on a highway to charge tolls for the lane’s users will have a certain benefit for many trips: a lower trip time. A new bus route may be convenient enough for some travelers to switch from driving to taking the bus, possibly reducing their trip cost.

© 2017 Steven Can Plan

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